Restless Leg Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD) are closely associated disorders also known as Myoclonus and Ekbom Syndrome, respectively. RLS and PLMD affect 2-8% of the population in the United States. Both conditions are characterized by involuntary movements of the limbs, most typically the legs.
RLS occurs during periods of wakefulness. PLMD occurs during sleep or in transitions from wakefulness to sleep or sleep to wakefulness. Patients with RLS or PLMD may suffer twitching, tingling, aching, burning, itching, or pulling sensations in their arms and/or legs. Patients with RLS often suffer from PLMD, but people with PLMD do not always have RLS. Because RLS patients may also suffer from sleep-related PLMD, these patients are often awakened, and their ability to return to sleep is delayed by RLS.
RLS patients are unable to sit still and may have to remain active to relieve limb discomfort. For patients suffering from RLS, relaxation and passive activities become increasingly problematic, adversely affecting quality of life.
For both PLMD and RLS patients, sleep quality deteriorates. When a patient tries to fall asleep, the leg discomfort begins. In severe cases, patients only sleep a few hours at night, resulting in excessive daytime sleepiness and disruption of the normal daily routine. RLS and PLMD patients often complain of irritability, anxiety, and depression. The severity of RLS and/or PLMD ranges from infrequent minor discomfort to daily agony that leads some patients to contemplate suicide.
Symptoms of PLMD may come and go through the night and over the course of one's life. PLMD episodes may last a few minutes or several hours. There may be an interval of days, weeks or months between episodes. PLMD patients may experience sudden but rhythmic limb jerks occurring periodically, e.g., every 20 to 40 seconds. PLMD episodes may be seen primarily in the first third of the night, during non-REM sleep. Patients with RLS often have PLMD, but patients with PLMD do not always have RLS. Polysomnographic studies indicate that about 70% to 90% of patients with RLS have PLMD.
PLMD movements may be characterized, for example, by periodic flexion of one or both legs involving bending at the hip and knee with upward bending of the foot and the great toe, resembling a flexion reflex. A normal healthy person may have five of these movements per hour. The diagnosis of PLMD is given when more than five movements per hour occur.
Both genders are affected, with a slightly higher incidence in women. These conditions are seen more commonly with advancing age. The prevalence of PLMD or RLS is 2% of the population of ages less than 30, 5% of ages 30 to 50, and 25% of ages 50-60. The highest prevalence is seen in age 65 or older, with 44% of the population affected. While usually diagnosed in older groups, these disorders may be traced to childhood. Hyperactive, fidgeting children or youths often labeled with “growing pains” may actually be showing the early manifestations of PLMD and RLS.